Elucidating interfacial parameters of platinum–palladium bulk alloy single crystals

Abstract

The application of mixed catalysts in chemical to electrical energy transformation reactions can be a strategy for enhancing the catalysis of these reactions. Platinum and palladium exhibit significant catalytic activity in reactions of different natures, influenced not only by composition but also by structure. The present work presents a fundamental study of the characterization and electrochemical behavior of platinum-palladium bulk alloy single-crystal electrodes (Pt_100−xPd_x), prepared via a modified Clavilier protocol. Electrodes with varying mass ratios of Pt and Pd, compositions ranging from 0 to 15% Pd, and crystallographic orientations of (111) and (100) were manufactured. X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) reveal a well-correlated bulk and surface composition with ordered crystalline structures. Cyclic voltammetry in HClO₄ and H₂SO₄ electrolytes indicates stronger anion interactions compared to pure platinum. Charge displacement experiments by CO adsorption estimate the effect of surface orientation and Pd content on the potential zero total charge (pztc). For Pt_100−xPd_x(111) surfaces, the pztc is very close to that of Pt(111), while surfaces with (100) orientation show decreasing pztc values with higher Pd content, favoring OH adsorption at lower potentials. Finally, the CO oxidation reaction on these Pt–Pd bulk alloy electrodes is studied by cyclic voltammetry, providing a profoundly comparative discussion of this reaction with Pt(111), Pt(100), and Pt(111) modified with Pd sub-monolayers.